U.S. Pat. No. 4,329,621, issued May 11, 1982 and assigned to the Assignee of the present application, provides a starter device for discharge lamps. Therein, first and second bimetal strips are connected to one another at one end forming a first switch contact. The opposite end of a first bimetal is connected to a source voltage terminal by way of a ballast and the opposite end of a second bimetal is connected to a discharge lamp. Also, a tungsten rod within the envelope forms a second contact immediately adjacent the first contact, and the tungsten rod and second bimetal are connected to opposite ends of a discharge lamp.
In operation, short-circuit current from a ballast passes through the first bimetal strip in an amount and for a time sufficient to cause flexure of the bimetal and separation of the normally-closed (N/C) first and second switch contacts. Thereupon, a pulse potential available from the ballast is applied by way of the bimetals to the discharge lamp in an amount usually sufficient to effect conduction thereof. Also, lamp current flowing through the bimetals is of an amount sufficient to maintain the first and second contacts in a separated positional location. Moreover, should the discharge lamp fail to ignite initially, the bimetals will cool and the contacts will close to again cause short-circuit current flow through the bimetals and a repeat of the above-described operation.
Additionally, the above-mentioned starting device is normally employed in a discharge lamp starting and operating circuit wherein a ballast coupled one of the bimetals to a voltage source terminal with the tungsten rod coupled to the other one of a pair of voltage source terminals. The discharge device is coupled to the other bimetal and to the tungsten rod or rigid conductive member.
Although the above-described starter apparatus and starting and operating circuitry does have numerous advantages over prior known structures and circuitry, it has been found that there are applications wherein a problem still exists. For example, it has been found that there are applications wherein the first and second switch contacts tend to stick to one another and fail to open in response to the flexure of a bimetal strip. Also, it has been found that switches having one rigid contact member tend to have a relatively short life span as compared with a flexible member. Moreover, the switches with a rigid contact appear to be much more sensitive to shock as compared with flexible members.